Graphene sheets have been proposed as a nanopore material, since the thinness of graphene allows good resolution of these base units.[2-4] The use of graphene as a nanopore membrane is an advance over nanopore sequencing work done in the last decade.[5] In the example shown in the figure, below, from a recent US patent, DNA is threaded through a nanopore in the gate of a field effect transistor.[6]

Graphene, which is an atomically-thin sheet of graphite, is highly conducting in its plane, but it insulates the regions on opposite sides of the sheet. A nanometer hole can be drilled in a graphene sheet using an electron beam, and the sheet can be used to separate solutions on opposite sides of the sheet. Although this is like the geometry of a Coulter counter,[7] the electrical conduction mechanism is different. Solution ions in the hole affect the sheet conductivity of the graphene, and DNA threaded through the holes displaces these ions to change the sheet conductivity.

While the signal-to-noise ratio for the ion current of graphene in DNA sequencing is just three, computer simulation found that the signal-to-noise ratio of molybdenum disulfide can be greater than fifteen.[8] Single layers of molybdenum disulfide also offer a different means of base detection, since the bases also impart a difference in transversetunneling current.[8] The nanopores can be crafted to give different edges containing a different combination of molybdenum and sulfur atoms to give an optimized signal strength.[8]

The computer simulations showed that four distinct signals are obtained from the four different bases in a double-stranded DNA molecule, while other systems have a problem distinguishing A from T and C from G. The University of Illinois research team is now investigating combinations of molybdenum disulfide with another material to produce a workable device.[9] Says graduate studentAmir Barati Farimani, who was the first author of the paper describing this research,

"The ultimate goal of this research is to make some kind of home-based or personal DNA sequencing device... We are on the path to get there, by finding the technologies that can quickly, cheaply and accurately identify the human genome. Having a map of your DNA can help to prevent or detect diseases in the earliest stages of development."[9]